The present invention relates generally to welding-type systems and, more particularly, to a system and method for delivering a welding-type consumable incorporating an electronically commutated motor (ECM) and an electronic commutator control.
Welding-type processes often use consumables, for example, metal wire, to aid in the welding-type process. Consumable delivery systems, such as wire feeders, are typically used to feed metal wire into a weld during a welding process such as Gas Metal Arc Welding (GMAW) and other welding processes. The performance of the consumable delivery system is paramount to the success of the welding-type process being performed. In the example of a wire feeder, precise and accurate delivery of the metal wire being fed to the weld is key to the welding type process. As such, high operational demands are placed on the wire feeder.
Typical wire feeders have a driven roller assembly for driving the consumable metal wire from a feed spindle through a welding gun for introduction to the weld. The drive mechanism in these driven roller assemblies are internally commutated direct current (DC) motors or brushed DC motors. Power is supplied to the brushed DC motor by a welding power source. The amperage or current delivered by the power source governs the speed in which the metal wire is fed to the weld. As such, the brushed DC motors are readily configured for speed control. Generally, the higher the amperage supplied to the wire feeder, the greater the speed by which the wire feeder supplies the metal wire to the weld.
However, performance demands on wire feeders and torches not only require accurate speed but also acceleration, deceleration, and break/breaking control. That is, the consumable wire must be accurately controlled during the welding process and immediately disengaged from the welding-type process upon termination of the process. Failure to accurately control delivery of the consumable wire can result in excessive spatter, puddling on the tip of the wire, and generally less accurate welding. Additionally, the puddling caused by inaccurate breaking may cause increased power consumption at restart.
To aid in the accurate delivery of the wire to the weld, some welders include welding torches incorporating wire delivery engines. In this case, the welding torch does not passively feed the wire through to the weld but includes another motor configured to receive the wire being fed to the torch and aid in its delivery to the weld. In such a case, the wire feeder motor and the torch motor must operate in concert to deliver the consumable metal wire. However, the aforementioned speed control based on amperage (or voltage) is inadequate to provide synchronization between the motors. That is, the design engineer must not only be concerned with delivery speed, but must also consider the torque associated with the delivery, else risk binding or bunching of the wire resulting from synchronization breakdowns between the wire feeder motor and the welding torch motor. As such, torque control of the motors is preferred to avoid such a breakdown.
However, torque control of brushed DC motors can only be achieved indirectly because commutation relying on control of internal brushes can only be controlled by augmenting the current (or voltage) supplied to the motor. As such, algorithms and systems have been developed whereby voltage or current control of the brushed DC motor is coordinated to simulate torque control of the motor. While such systems are able to replicate torque control, responsiveness remains less than desirable.
Accordingly, it would be desirable to have a system and method for improved accuracy and control of welding-type consumable delivery. Furthermore, it would be desirable to incorporate a motor for consumable delivery that can be controlled using torque control schemes for improved control and synchronization between consumable delivery motors. Also, it would be advantageous to have improved accuracy in wirefeed speed control to avoid excessive spatter and weld tip build up.